This invention pertains to stabilized optical systems and more particularly to such systems employing an offaxis stabilizer.
An optical system which provides magnification, such as binoculars or a telescope, will tend to exaggerate in the image produced any physical disturbance which is imparted to the system itself during viewing. As a consequence, higher powered optical systems (e.g., beyond 7.times. magnification) are frequently not practical without some means of stabilization to cancel such effects, since vibration, muscular movements of the operator, etc. will distort the images viewed to such an extent that they are not perceptible. Consequently, it is necessary to compensate for these vibrations in high power optical systems, especially where such systems are to be used in areas of high vibration or frequent motion, such as aboard a ship or an aircraft.
One technique which may be utilized to achieve a stabilized image is to isolate the entire optical system from the perturbing motion. This has been done in the prior art, but such a solution tends to be expensive and to require a large and bulky apparatus. Therefore, others have attempted to solve the stabilization problem by isolating some component within the optical train of the system. When one optical component is isolated from the disrupting motion, the consequent motion of that component relative to the remainder of the system will tend to compensate for the disturbance imparted to the viewed image by the remaining parts of the optical system.
This method of component isolation may be illustrated by reference to a typical optical system of interest, such as that of a binocular or monocular. Such optical systems normally include an objective lens group, an eyepiece lens group, and an intermediate optical element. The intermediate element, which is frequently made up of one or more prisms, is added to the system to correct for the inversion and reversion of the image which is caused by the optical action of the objective and eyepiece lens groups.
In binoculars and monoculars, the eyepiece lens group is not considered a practical candidate for stabilization isolation because it should be held stationary and close to the eye of the viewer. Furthermore, although the stabilization of the objective lens group in such systems has been attempted, it has been generally recognized by those skilled in the art that the most desirable solution to the stabilization problem is to isolate the intermediate element, i.e., the inverting and reverting prism or prisms. Stabilized systems of this type are known, typical examples being described and illustrated in U.S. Pat. No. 4,013,339, issued Mar. 22, 1977 to Ando et al., entitled "Optical Image Stabilizing System"; and in an article by David B. Fraser entitled "Design of a Low Cost, High Magnification, Passively Stabilized Monocular, the Stedi-Eye", appearing in Vol. 39 of the SPIE Proceedings, August, 1973. The teachings of each of the above publications are hereby incorporated by reference into this application.
Various techniques for stabilizing the intermediate optical element in binocular and monocular systems have been proposed, including gyrostabilized central afocal devices, programmed stabilization employing hydrostatic techniques, tuned and dampened isolators using springs and bearings, and axially oriented inertial stabilization systems, as shown in U.S. Pat. No. 4,013,339, mentioned above. All of the various techniques which are known in the art, however, suffer from disadvantages. Some of these devices, for example, utilize inertial elements which are aligned with the optical train. These devices, as a result, require specially fabricated optical elements, such as lenses which may be rotated, etc. As a consequence, such devices tend to be inordinately expensive to manufacture and, furthermore, tend to extend the overall length of the optical train, which may be undersirable in some applications, as when the device is to be hand held and portable. Other stabilizing devices known in the art utilize an off-axis stabilizing element such as a gyroscope, connected through some form of linkage to an optical element. Previous off-axis stabilizer designs, however, have incorporated resilient members into the linkage between the inertial element and the stabilized optical element in order to compensate for the nutational and precessional motions of the gyroscope. Because of the compliance introduced by such resilient members, a highly accurate alignment of the optical element may not always be achieved in such designs and a deteriorated image may result.
Therefore, a need has developed in the art for an improved stabilized optical system incorporating an off-axis stabilizer.
Furthermore, it would be advantageous to provide such a system with a rigid connecting linkage between the stabilized optical element and the off-axis stabilizer to consistently maintain the accurate alignment of the optical element.
In addition, it would be advantageous to provide such a system with nutational damping and precessional compensation which would not degrade the stabilized image produced by the optical system.
It would also be advantageous to provide such a system in a compact and lightweight package that is highly portable.
In addition, it would be advantageous to provide such a system with a shortened optical train to enhance the convenience and portability of the system.